Product scanning system and method

ABSTRACT

A system in which a succession of products ( 12 ) to ( 16 ) traverse a gap between two conveyors ( 10, 18 ), comprises a ring ( 32 ) carrying an array of one or more equi-spaced laser displacement transducers ( 36-42 ) connected to a computer ( 48 ). The ring is disposed perpendicular to the direction of product movement, such that each product (e.g. a log of food) passes through its central region, the ring being rotatable in a continuous or oscillatory manner. Signals received by the computer from the transducers are stored and computed to determine the shape and/or size of the product to enable the product to be cut into an optimum number of pieces. A method is described for determining volume and thereby weight using mean density values for the products, of irregularly shaped bulk product, particularly fresh meat.

FIELD OF INVENTION

This invention concerns product scanners, particularly scanners to beused in conjunction with product handling apparatus such as cutting orslicing apparatus and especially such apparatus when employed to cut orslice bulk foodstuffs.

BACKGROUND OF THE INVENTION

In many processes where randomly shaped raw material in bulk form is tobe cut into portions, it is desirable to be able to feed to a controlsystem information concerning the geometry and topography of the bulkmaterial before it passes to the cutting step in the process. Suchinformation can enable a control system to calculate where to positionthe raw material correctly for the cutting operation and to optimise theprocess to produce the best yield of cut portions from the bulk.

Scanning methods are known whereby product moving along a conveyor isviewed by a TV camera and the information is fed to a computer formingpart of a process control system. The accuracy of such systems has notallowed cutting controls signals to allow optimal division of bulkproduct such as fresh meat, into portions of appropriate size and weightideal for retailing.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a system is providedin which product traverses an inspection region at a defined positionalong a conveyor means and at least one distance measuring transducer ismounted for movement around the region in a plane (the inspection plane)generally perpendicular to the movement of the product therethrough, andthe distance from the transducer to each of a succession of points onthe product surface in the inspection plane is determined by computermeans supplied with signals from the transducer and the values arestored and used in a computation to determine at least the shape and/orsize of the cross-section of the product in the inspection plane.

Where the product is relatively rigid such as frozen bulk food, it isgenerally necessary to inspect the surface of the product through 360°.

Where access to the whole surface is required the inspection plane needsto be at a discontinuity in the conveyor means—typically a gap betweentwo conveyors.

Where full 360° access is not required the conveyor means can if desiredextend continuously through the region.

Where the product is not rigid such as fresh meat, the underside of theproduct will tend to conform to the surface on which it rests. In thecase of a conveyor this may be flat or dished to form a trough in linewith the conveyor length direction.

Provided the conveyor surface shape is known (and it can be determinedif desired by the transducer and computing means without product in theinspection plane) the inspection of the product surface can berestricted to the free surface of the product which if the conveyor iscontinuous through the inspection station will in any case be fullysupported over the whole of its underside which can be assumed toconform to the surface of the conveyor. If (as may be desirable toaccommodate cutting blades or saws or simply to render the system ableto handle rigid frozen product as well as fresh floppy product) a narrowgap exists in the inspection plane between two conveyors which comprisethe conveyor means, one feeding product to the inspection station andthe other conveying it away in the same general direction as it isdelivered thereto, the underside of the product can still be consideredto be the same shape as that of the upper surface of each of theconveyors, thereby obviating the need for the transducer to “inspect”the underside of the product where it bridges the narrow gap.

The time required to scan the cross-section can be reduced by using aplurality of transducers equally spaced around the inspection region sothat less than 360° of movement is needed for the transducers in orderfor the whole of the surface in the said region to be inspected.

Where less than 360° inspection of the surface is required, typicallyonly 180° because the underside surface is assumed to be known, theprocess can be further speeded up by rotating the single transducer or aplurality of equally spaced apart transducers through just sufficient ofan angle for all the surface which needs to be inspected to be seen bythe transducer or transducers.

According to a preferred feature of the invention, the transducer ortransducers are rotated first in one sense and then back in an oppositesense to the same extent, so that flexible cable connections may be madebetween the transducer or transducers and a stationary computing means.

The shape and/or size value for the product cross-section may be storedfor each of a succession of positions of the product relative to theinspection region, to enable the volume of the product to be determinedby a further computational step.

Preferably signals are generated when a length of product enters andleaves the inspection region and to this end proximity or movementsensors may be provided at appropriate positions along the conveyormeans, or the inspection transducer or transducers and the computationmeans may be programmed to produce product arrival and product departuresignals.

In one embodiment transducers are located at 90° intervals around theinspection region, for movement in synchronism and the movement may becontinuous or oscillatory, so as to inspect the whole of the surface ofproduct.

Thus for example laser displacement transducers may be mounted at 90°intervals around a ring and positioned so that they direct their beamsthrough a gap between two in line conveyors, and the ring may be drivenin rotation by a servo motor.

Conveniently the servo motor is controlled by a computer, whichconveniently is employed also to perform the computation on thecross-section data gathered from the transducer(s).

Preferably four such transducers are arranged equally spaced around thering and the output of each of the transducers is logged by the computermeans.

Where only a single transducer is employed it is necessary to rotate itaround the whole of the arc over which inspection is required, and iffull 360° inspection is required, the arc must extend around a full 360°centered on the product.

If the arcuate movement of the transducer or transducers is fast enoughin relation to the linear movement of the product, the locus of theinspection point around the surface of the product is a closed pathsimilar to the line which will be produced if a very thin knife were tohave sliced through the product leaving the two cut surfaces abutting.If the product happened to be of a circular cross-section, and theproduct is stationary or the transducer speed of rotation is very fastrelative to the linear speed of the product, the locus of the inspectionpoint will be a closed circle.

If the rotation is not fast enough, the locus of the point will describea continuous path somewhat in the form of a helix, the cross-sectionalshape of which will be determined by that of the product log. Only atrue helix will occur in the case of product whose cross-section iscircular. The “helical” type of path is that which will normally beobtained.

A true cross-section can be obtained if the movement of the product isintermittent, so as to move relative to the transducer(s) in a series ofsteps, and where the output of the transducer(s) is only used when theproduct is stationary, or the transducer(s) is/are switched so as onlyto be active when the product is stationary.

In a preferred embodiment for use with fresh meat bulk product, threetransducers are arranged equidistantly around an arc centred on theinspection region so that it is only necessary for the array to rotatethrough 60° for the entire upper surface of the bulk product to betraversed by the three transducer inspection spots, thereby reducing theadvance of the “helix” per scan, and allowing either a greater linearspeed of the product through the inspection plane or a higher samplingrate of the bulk product cross-section and therefore a more accuratedescription of each product cross-section to be obtained. By oscillatingthe array back and forth through 60° and scanning during both forwardand reverse movements of the transducer array the whole of the uppersurface of the product can be scanned by the transducer light spots asit passes through the inspection plane.

An arc containing three transducers typically extends around 120° C.

If six transducers were mounted equidistant around a 150° arc, thesampling rate, or the linear product speed, can be doubled, since it isonly necessary to rotate the array through 30° for all the circumferencewhich is to be inspected, to be seen.

Where it is desirable that the transducer or transducers is/are torotate continuously, slip ring connections may be employed, or one ormore low power radio transmitter devices may be associated with thetransducer array for transmitting transducer output signals as amodulation of a radio signal to a nearby stationary receiver, from whichthey are conveyed to a computer means.

Where one transmitter is mounted on an array of two or more transducers,the output of each transducer may be transmitted on a different channel,or time division multiplexing, or any other multiple channel techniquemay be employed, to transmit the two or more transducer output signalsto one or more radio receivers adapted to decode the received signal orsignals to allow the distance data to be derived from the received radiosignals for input to the computer means.

The conveyor means may also be driven by at least one servo motor whichmay also be controlled from the computing means in a similar way to theservo motor driving the transducer array, and the or each conveyor servomotor is synchronised to provide reliable transfer of product from oneconveyor to the other across any gap. Preferably the computer controlalso synchronises the transducer scanning servo motor in relation to theconveyor motion.

Sensors may be provided to deliver feedback signals to the computer toindicate actual movement of the conveyor and/or transducer(s), toprovide a form of closed loop servo control and to indicate to thecomputer when product is about to enter or leave the inspection plane orany interruption in either movement occurs.

According to another aspect of the invention there is provided a methodof determining the volume of a length of bulk product having a varyingcross-section, comprising the steps of linearly moving the productthrough an inspection plane which extends generally perpendicular to thelinear movement of the product by motor-driven conveyor means, moving adistance measuring transducer along an arcuate path in the inspectionplane, computing the length of the product by reference to its linearspeed past at least one detector which may be the transducer ortransducers, and computing the distance from the transducer to each of asuccession of points around the product surface in the inspection plane,and computing therefrom the area of the cross-section defined by thesaid points, and where these do not extend completely around the productcross-section, employing stored data about the shape of the surfacesupporting the bulk product in, or just upstream or downstream of theinspection plane, to provide a complete set of data by which to computethe cross-sectional shape and/or area, determining the increments ofvolume of bulk product attributable to each transducer scan by referenceto the distance moved by the product before the next scan, andsummarising the increments of volume over the whole of the length of thebulk product as it progresses through the inspection plane.

The method also comprises the steps of scanning the conveyor supportsurface in the inspection plane and storing data relating thereto, whenproduct is absent.

The weight of the bulk product can be computed by employing a meandensity value and multiplying volume by mean density, and an example ofsuch a process to which the invention can be applied is one in which alog of fresh meat is to be fed into a cutting machine in which theposition and/or angle of each cut determines the size and/or weightand/or volume and/or shape of the severed portions. Using the inventionportions of constant weight or constant volume or a particular shape canbe cut from any particular lump of meat, and/or the volume/shape/weightmay be adjusted so as to produce the optimum number of steaks and endpieces from the bulk.

Other applications lie in the field of grading product, where product issorted weight, volume, length etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawing, in which:

FIG. 1 illustrates diagrammatically apparatus comprising a scanningsystem embodying the invention for inspecting the cross-section of logsof foodstuff such as meat or fish;

FIG. 2 is a end view of the apparatus of FIG. 1; and

FIG. 3 in a modification of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings a conveyor 10 supplies logs of product such as 12, 14,16 to a second main conveyor 18, and in doing so causes each log totraverse a small gap 20 between the end of conveyor 10 and the beginningof conveyor 18.

The exit from conveyor 10 is defined more precisely than would be thecase if end roller 22 alone served this purpose, by virtue of a jockeyroller 24 of smaller diameter, positioned so as to extend the horizontalsurface of the infeed conveyor 10 further towards roller 26 of theoutfeed conveyor 18 than would otherwise be the case.

A similar jockey roller (not shown) may be employed in a similar fashionat the entry end of the outfeed conveyor 18, if desired.

Servo motors 28 and 30 drive conveyors 10 and 18 respectively.

Around the gap 20 is located a circular ring 32 which is rotatableeither continuously or in an oscillatory manner by a servo motor 34. Theplane of the ring 32 is generally perpendicular to the line of directionof movement of the conveyors, and the horizontal surface of the conveyorextends through the central region of the ring so that product carriedthereon is also located at the centre of the ring.

Mounted at equally spaced apart points around the ring 32 are fourdistance measuring transducers 36, 38, 40 and 42 respectively, eachbeing directed radially inwards so as view an elemental region of thesurface of any product bridging the gap 20. As shown, the product “log”14 bridges the gap, and the elemental areas of the surface seen bytransducers 36 and 38 are shown at 44 and 46 respectively.

Although the transducers 36 to 42 are capable of accurately measuringdistance over a significant range, where the apparatus is to handleproduct of significantly differing cross-sectional size, provision maybe made for adjusting the position of the ring 32 relative to the twoconveyors 10, 18 so as to accommodate larger cross-sectional productwithin the central area of the ring, and where desirable to position thecentre of the cross-section of the product log as near as possible tothe centre of the ring.

By way of example, the transducers 36 to 42 may be laser displacementtransducers of the type manufactured and supplied by Keyence Corporationof the USA, such as those forming the LB-1000 Series, and in particulartypes LB-301 and LB-1201 which are capable of measuring distances in therange 200-400 mm. Reference is made to the Keyence LB-1000 SeriesInstruction Manual for operational and connection details for suchdevices.

A system control and log measuring computer 48 receives distance signalsfrom the transducers 36 to 42 as first inputs, possibly via a radio linksuch as formed by transmitter 50 and receiver 52, and also informationas input signals from transducers 54, 56 and 58 on the motors 28, 30 and34 respectively, and optionally from proximity sensors or the like at 60and 62, to indicate the arrival and departure of logs such as 14 intoand out of the plane of the ring 32.

The computer 48 also provides output signals to a motor controller 64which in turn controls the supply of electric current to each of themotors 28, 30 and 34.

The motor 34 may be controlled by the computer so as to rotate first inone sense and then the other so as to oscillate the ring 32 through a90° arc as shown by the double ended arrow 66.

It is to be understood that if only two transducers are mounted at 180°apart around the ring then the oscillatory motion would have to be 180°,and if only one transducer is mounted around the ring, the oscillatorymotion would have to be a full 360°.

It is to be noted that the number of transducers will determine thelength of arc of the oscillatory motion, and the greater the number oftransducers the smaller will need to be this arc.

The computer also provides a data output to a printer or other outputdevice 68 to allow a record to be kept of the computed areas and/orvolumes of the logs in the same order as they move one after anotherthrough the gap 20.

The computer also provides data output to a process control system whichprovides control signals for a cutting machine such as a guillotine orbandsaw (not shown) which is supplied with logs of product 16, 14, 12 inturn from the output of the conveyor 18.

A weighing scale may be incorporated into the apparatus such as thatshown at 72 at the infeed end of the apparatus. It is to be understoodthat if a weighing scale is incorporated it can be incorporated at anyconvenient point and does not necessarily have to be incorporated in theinfeed end.

FIG. 2 merely shows the apparatus of FIG. 1 from the infeed end andshows the preferred oscillatory motion of the ring 32.

In operation, as a log of food product travels along the conveyor, itpasses through the laser beams as it traverses the gap between theconveyors. The scan servo motor 34 causes the laser transducersupporting ring 32 to oscillate through 90°.

The output of each of the four laser transducers 36, 38, 40 and 42varies proportionally with its distance from the point from which itsbeam is reflected from the surface of the log, such as 44 or 46.

By measuring and recording the output of each of the transducers 36 to42, and logging that data relative to the known angular position of thelaser assembly (derived from the transducer 58 of scan drive servo 34and the known linear position of the product derived from the transducer54 of infeed servo 28, for example), so a full three-dimensional map ofeach product log such as 14 can be built up in a memory within thecomputer 48.

Scan patterns are infinitely variable from straight line (in which thescan servo 34 is stationary) to circular (where the conveyor servos 28,30 are stationary) with a helical type of scan of variable angledepending on the relationship between the rotational speeds of thevarious motors lying between these two extremes.

Other information may be added to the data to be stored in the processcontrol computer 48, such as the length and/or weight of each log and/orthe total weight of N logs of food product derived from weighing cell72, enabling the computer to determine parameters to be applied tosubsequent process steps.

The lengths of the logs may be obtained by inspecting the output signalsof one or more of the laser transducers or from signals from sensorssuch as 60 and 62, or where it is known that no slip occurs, from therotation of the conveyor drives 28 and 30. Referring now to FIG. 3,there is shown a modification of the apparatus of FIG. 1 in whichsimilar parts are indicated by the same reference numerals.

Spaced by a narrow gap 76 from the main conveyor 18 is a third outfeedconveyor 78. A long guillotine blade 80 driven by a motor 82 ispositioned to pass through the gap so as to slice the product, in thiscase a log of meat 84, into individual slices or portions 86. Since thespeed of the conveyor 78 is higher than that of the main conveyor 18,the portions are separated from one another as they drop onto theconveyor 78.

In this arrangement the length of a log traversing the gap 20 betweenconveyors 10 and 18 is calculated by the computer 48 from a signal fromthe motors 28 and 30 (which normally drive the conveyors at the samespeed), indicating the actual speed of the conveyors, and from signalsfrom the transducers 36 to 42 indicating the entry and exit of the login passing across the gap 20. By thus computing the volume of the log,and having input into its memory store a constant figure for the averagedensity of the product, so the weight of the log can be determined.

The computer 48 is also connected to the motor 82 to control theoperation of the blade 80. A variety of programs can be input to thecomputer to achieve optimum sliced portions of product, eg of theconstant thickness or weight. For example, the program can automaticallyalter the slice thickness due to variation in the profile orcross-section of the log, as determined by the transducers, so as toobtain constant weight portions.

The transducers also serve to indicate the actual position of a log onthe conveyors 10 and 18 so that, in the absence of slip, the preciseposition of the log can be determined by the computer 48 when it reachesthe blade 80. The gap 20 shown in FIG. 3A between the conveyors 10 and18 and the provision of a 360° rotatable scaning array, allows thetransducer to “see” all round the bulks of product. In the alternativearrangement of FIG. 3B, in which the conveyor extends continuouslythrough the inspection region transducers are now only required abovethe conveyor as shown in FIG. 3B.

What is claimed is:
 1. A method of determining the volume of a length offloppy bulk product having a varying cross-section, comprising the stepsof: (1) placing the product on a supporting surface provided by amotor-driven conveyor, (2) linearly moving the product through aninspection plane which extends generally perpendicular to the linearmovement of the product by the motor-driven conveyor, (3) moving atleast one distance measuring transducer in the inspection plane along anarcuate scanning path which extends in the inspection plane only arounda part of the product cross-section which included an unsupportedsurface region of the product, (4) computing the length of the productby reference to its linear speed or position past a detector, (5)computing distance from the transducer to each of a succession of pointsaround the unsupported surface region of the product in the inspectionplane, (6) storing data as to shape of the supported surface region ofthe product, (7) computing from said distances and said data the area ofthe cross-section of the bulk product in the inspection plane, (8)determining the increments of volume of bulk product attributable to asuccession of transducer scans by reference to the distances moved bythe product between successive scans, and (9) summing the increments ofvolume over the whole of the length of the bulk product as it progressesthrough the inspection plane.
 2. A method as claimed in claim 1, whenmodified to determine the weight of bulk product by the steps ofproviding a mean density value and multiplying the computed volume bythe mean density value.
 3. A method as claimed in claim 2, when appliedto a log of fresh meat which is to be fed into cutting machine, in whichat least one of the position and angle of each cut determines at leastone of the size and weight and volume and angle shape of the severedportions, and wherein computer means determines the positions at whichthe log is to be cut from the data derived from the transducer to enablea portion of one of constant weight, constant volume, and a particularshape to be cut from the log of meat, and adjusting one of the volume,shape and weight to produce the optimum number of steaks and end piecesfrom the log of meat.
 4. A method as claimed in claim 3, wherein thecomputer determines the positions at which the log is to be cut so as toproduce an optimum number of steaks and end cuts from the log of meat,with reference to a preferred volume or shape or weight or combinationthereof.
 5. A method as claimed in claim 1, wherein the conveyor extendsthrough the inspection plane and the shape of the underside surface ofproduct which is to be conveyed therethrough by the conveyor isdetermined by scanning the surface of the conveyor by the transducer ata time when there is no product in the inspection plane, and storingdata relating to the shape and position of the upper surface of theconveyor where it extends through the inspection plane to be usedsubsequently as data defining the underside of product located thereonin the plane.
 6. Apparatus for determining the volume of a length offloppy bulk product having a varying cross-section comprising: (1) aproduct-supporting surface provided by a motor-driven conveyor, (2)means for driving the conveyor linearly to move the product through aninspection plane which extends generally perpendicular to the linearmovement of the product by the motor-driven conveyor, (3) means formoving at least one distance measuring transducer in the inspectionplane along an arcuate scanning path which extends in the inspectionplane only around a part of the product cross-section which included anunsupported surface region of the product, (4) a detector, (5) means forcomputing the length of the product by reference to its linear speed orposition past the detector, (6) means for computing the distance fromthe transducer to each of a succession of points around the unsupportedsurface region of the product in the inspection plane, (7) means forstoring data as to shape of the supporting surface, (8) means computingfrom said distances and said data the area of the cross-section of thebulk product in the inspection plane, (9) means for determining theincrements of volume of bulk product attributable to a succession oftransducer scans by reference to the distances moved by the productbetween successive scans, and (10) means for summing the increments ofvolume over the whole of the length of the bulk product as it progressesthrough the inspection plane.
 7. A system as claimed in claim 6comprising an array of three transducers arranged equidistantly aroundsaid path, and means to rotate the array through 60° to inspect theentire upper surface of the product thereby enabling inspection at oneof a higher sampling rate and a greater linear product speed.
 8. Asystem as claimed in claim 6 in which the said at least one distancemeasuring transducer comprises a laser displacement transducer.